The invention relates to switched reluctance ("SR") motors and, more particularly, to an apparatus for determining which phase of an SR motor to commutate at a given moment.
SR motors have multiple poles on both the stator and the rotor. There are windings or coils on the stator poles and each pair of windings on diametrically opposite stator poles is connected in series to form an electrically independent phase of the SR motor. There are no windings or magnets on the rotor. However, the rotor is made of a magnetically permeable material such as, for example, a ferrous alloy.
In order to energize or commutate an SR motor, it is necessary to first determine the position of the rotor with respect to the stator. The position of the rotor with respect to the stator establishes which phase of the stator should be energized at a given moment. If the position of the rotor is not correctly determined, commutation of one of the stator phases may result in inefficient motor operation or braking of the rotor. However, many conventional sensors for determining the rotor position at a given moment are bulky, unreliable and expensive.